A wireless network includes a radio access network and a core network. A core network of a long term evolution (LTE) wireless network includes an MME. The MME has functions similar to those of a service general packet radio service (GPRS) support node (SGSN) of a second/third generation (2G/3G) network, and is mainly responsible for mobility management and user authentication. When a UE is in an idle state in a 2G/3G or LTE wireless network, the UE needs to respectively negotiate a non-access stratum (NAS) security capability with the SGSN or the MME. The security capability includes an NAS signaling encryption algorithm, a corresponding NAS integrity protection key Knas-int, an NAS integrity protection algorithm, and a corresponding NAS confidentiality protection key Knas-enc, which are used for signaling transmission between the UE and a system, thereby ensuring the normal receiving of the UE signaling and the security of the communication system.
When the UE accessing a 2G global system for mobile communications (GSM) edge radio access network (GERAN) or a 3G universal mobile telecommunications system (UMTS) terrestrial radio access network (UTRAN) moves in the idle state, the UE may move to a tracking area of an LTE radio access network, and thus the UE may access the network again through the LTE. At this time, a tracking area update (TAU) procedure occurs, that is, a TAU procedure between heterogeneous networks occurs. During the procedure, since the entity performing security capability negotiation for the UE changes, for example, from the SGSN to the MME, and the entities may have different security capabilities, the security capability negotiation procedure needs to be performed again, so as to ensure the security of subsequent interaction between the UE and the network. It should be noted that, for the LTE network, the security capability negotiation includes negotiation of an NAS confidentiality protection algorithm and an NAS integrity protection algorithm, a radio resource control (RRC) confidentiality protection algorithm and an RRC integrity protection algorithm, and a user plane (UP) confidentiality protection algorithm.
For the TAU procedure initiated by the UE in the idle state, the negotiation of the NAS confidentiality protection algorithm, the NAS integrity protection algorithm, and the corresponding NAS protection keys need to be solved.
During the implementation of the present invention, the inventor found that, no method for negotiating the security capability during the TAU procedure between the heterogeneous networks can be found in the prior art, so that when the UE moves from the 2G/3G network to the LTE network, the security capability negotiation cannot be performed, resulting in that the security of subsequent interaction between the UE and the network cannot be ensured.